Oracle Update There must be an update that you don't know about.

Basic Update Statements
The Oracle UPDATE statement processes one or more rows in a table and sets one or more columns to the values of you specify.
Update All records	UPDATE <table_name> SET <column_name> = <value>
	CREATE TABLE Test AS SELECT object_name, Object_type From All_objs; SELECT DISTINCT object_name From Test; UPDATE Test SET object_name = ' OOPS '; SELECT DISTINCT object_name From Test; ROLLBACK;
Update a specific record	UPDATE <table_name> SET <column_name> = <value> WHERE <column_name> = <value>
	select DISTINCT object_name from Test update test set object_name = ' LOAD ' COMMIT; SELECT DISTINCT object_name from test
Update based on a queried value	UPDATE <table_name> SET <column_name> = ( SELECT <column_name> From <table_name WHERE <column_name> <condition> <value>) WHERE <column_name> <condition> <value>;
	CREATE TABLE Test AS SELECT table_name,CAST ("as VARCHAR2 ()) as Lower_name From User_tables; DESC Test SELECT * From Test WHERE table_name like '%a% '; SELECT * From Test WHERE table_name not like '%a% '; --This was not a good thing ... UPDATE Test T SET Lower_name =( SELECT DISTINCT LOWER (table_name) From User_tables u WHERE U.table_name = T.table_name and u.table_name like '%a% '); -Look at the number of rows updated SELECT * from Test; --neither is this  UPDATE Test T SET lower_name =  (   SELECT DISTINCT LOWER (table_name)   from User_tables u   WHERE u.table_name = T.table_name   U.table_name not like '%a% ' ) ; select * from Test; update test t set lower_name =  (   Select DISTINCT LOWER (table_name)   from User_tables u   WHERE u.table_name = t.table_name   and U.table_name Like '%a% ' WHERE t.table_name like '%a% '; SELECT * from test;
Update based on a query returning multiple values	UPDATE <table_name> <alias> SET (<column_name>,<column_name> ) = ( SELECT (<column_name>, <column_name>) From <table_name> WHERE <alias.column_name> = <alias.column_name>) WHERE <column_name> <condition> <value>;
	CREATE TABLE Test AS SELECT T. table_name, T. tablespace_name, S.extent_management From User_tables T, user_tablespaces s WHERE T.tablespace_name = S. tablespace_name and 1=2; DESC Test SELECT * from Test; --Does not work UPDATE Test SET (table_name, tablespace_name) = ( SELECT table_name, Tablespace_name from User_tables); --Works INSERT into Test (TABLE_NAME, Tablespace_name) SELECT table_name, Tablespace_name From User_tables; COMMIT; SELECT * From Test WHERE table_name like '%a% '; --Does not work UPDATE Test T SET tablespace_name, extent_management = ( SELECT Tablespace_name, Extent_management From User_tables A, user_tablespaces u WHERE T.table_name = A.table_name and a.tablespace_name = U.tablespace_name and t.table_name like '%a% '); --Works but look at the number of rows updated UPDATE Test T SET(Tablespace_name, Extent_management)= ( SELECT DISTINCT U.tablespace_name, u.extent_management From User_tables A, user_tablespaces u WHERE T.table_name = A.table_name and a.tablespace_name = U.tablespace_name and t.table_name like '%a% '); ROLLBACK; --works properly update test T set  tablespace_name ,  extent_management )  =  (   Select Distinct  ( u.tablespace_name,  U.extent_management   from User_tables A, user_ tablespaces u   WHERE t.table_name = a.table_name   and a.tablespace_name = U.tablespace_name Span style= "color: #0000ff;" >) WHERE t.table_name like '%a% '; SELECT * from test;
Update The results of a SELECT statement	update (<select statement>) SET <column_name> = <value> WHERE <column_name> <condition> <value
	SELECT * From Test WHERE table_name like '%a% '; SELECT * From Test WHERE table_name not like '%a% '; UPDATE ( SELECT * From Test WHERE table_name not LIKE '%a% ') SET extent_management = ' Unknown ' WHERE table_name not like '%a% '; SELECT * from Test;
Correlated Update
Single Column	update TABLE (<select statement>) < Alias> SET <column_name> =  (   SELECT <column_name>   from <table_name> <alias>   WHERE <alias.table_name> = <alias.table_name> ) ;
	conn hr/hr CREATE TABLE empnew as SELECT * FROM Employees; update empnew set salary = Salary * 1.1; update employees t1 set salary =  (   SELECT salary   from Empnew t2   Where t1.employee_id =  t2.employee_id ) ; drop table empnew;
Multi-column	update <table_name> <alias> SET ( <column_name_list>) = (   SELECT <column_name_list>   from <table_name> <alias   WHERE <alias.table_name> <condition> <alias.table_name>);
	CREATE TABLE T1 AS SELECT table_name, Tablespace_name From User_tables WHERE RowNum < 11; CREATE TABLE T2 as SELECT table_name, TRANSLATE (tablespace_name, ' aeiou ', ' VWXYZ ') as Tablespace_name From User_tables WHERE RowNum < 11; SELECT * from T1; SELECT * from T2; UPDATE T1 T1_alias SET (table_name, tablespace_name) = ( SELECT table_name, Tablespace_name From T2 T2_alias WHERE t1_alias.table_name = t2_alias.table_name); SELECT * from T1;
Nested Table Update
	See Nested Tables page
Update with returning Clause
Returning Clause Demo	UPDATE (<select statement>) SET .... WHERE .... Returning <values_list> Into <variables_list>;
	Conn HR/HR var bnd1 number var bnd2 VARCHAR2 (30) var bnd3 number UPDATE Employees SET job_id = ' Sa_man ', salary = salary + 1000, department_id = 140 WHERE last_name = ' Jones ' Returning salary*0.25, last_name, department_id Into:bnd1,: Bnd2,: Bnd3; Print Bnd1 Print Bnd2 Print Bnd3 Rollback
	Conn HR/HR Variable bnd1 number UPDATE Employees SET Salary = Salary * 1.1 WHERE department_id = 100 Returning SUM (Salary) into : bnd1; Print Bnd1 Rollback
Update Object Table
Update a Table Object	UPDATE <table_name> <alias> SET VALUE (<alias>) = ( <select statement>) WHERE <column_name> <condition> <value>;
	create TYPE People_typ as OBJECT ( last_name     VARCHAR2 (+), department_id number (4), salary         number (8,2)); / CREATE TABLE people_demo1 of People_typ; Desc people_demo1 CREATE TABLE people_demo2 of People_typ; Desc PEOPLE_DEMO2 INSERT into People_demo1 VALUES (People_typ (' Morgan ', ten, 100000)); INSERT into People_demo2 VALUES (People_typ (' Morgan ', ten, 150000)); update people_demo1 p set VALUE (P) =   (   select value (q) from People_demo2 Q   WHERE p.department_id = q.department_id ) where p.department_id = ten; SELECT * from People_demo1;
Record Update
Update based on a record Note:this construct updates every column so use with care. May cause increased redo, undo, and foreign key locking issues.	UPDATE <table_name> SET ROW = <record_name> WHERE <column_name> <condition> <value>;
	CREATE TABLE T as SELECT table_name, Tablespace_name From All_tables; SELECT DISTINCT Tablespace_name From T; DECLARE TREC T%rowtype; BEGIN Trec.table_name: = ' DUAL '; Trec.tablespace_name: = ' new_tbsp '; UPDATE T SET ROW = Trec WHERE table_name = ' DUAL '; COMMIT; END; / SELECT DISTINCT Tablespace_name From T;
Update partitioned Table
Update only records inch a single partition	UPDATE <table_name> PARTITION (<partition_name>) SET <column_name> = <value> WHERE <column_name> <condition> <value>;
	Conn Sh/sh UPDATE Sales PARTITION (sales_q1_2005) s SET s.promo_id = 494 WHERE amount_sold > 9000;

(http://blog.csdn.net/zgying/article/details/6264161)

Oracle Update There must be an update that you don't know about.